1. Field of the Invention
The present invention generally relates to a high-speed dynamic actuating system for optical disks, and more particularly, to an actuating system, wherein there is provided a closed-loop system together with a lens controller and a sledge controller so as to achieve high-speed track-jumping and thus improve the operation quality and reduce the fabrication cost.
2. Description of the Prior Art
Recently, due to the fast development in electro-optic technology, the related techniques of optical disk drives have grown rapidly and compatible with multimedia applications. In particular, CD-ROMs provide a great amount of data storage, and a new disc called DVD-ROM (digital video disk) provides considerably more data storage, reaching data storage capacities of up to 17 GB as compared to 680 MB for a CD-ROM. Such devices have especial usefulness in the storage of archiving data and in the storage of video data, such as full-length movies, and therefore have become the most widely used peripheral components not only in computer-based systems but also in Hi-Fi audio/video systems. At present, in the technical fields according to optical disk drives, it is crucial to fulfill precise track-accessing with a high speed. The convention open-loop track-jumping takes a long period of time to perform segmental adjustment. There exists a serious problem in that the diversity between devices can not be overcome. However, the present invention provides a closed-loop approach that can effectively solve the problem.
On the other hand, the pick-up head that an optical disk drive uses is different in configuration from that in a hard disk. Consequently, the track-jumping time in an optical disk drive differs from that in a hard disk. Moreover, the wobble of the lens is another problem that is difficult to prevent. It is thus the motive for the present invention to activate the pick-up head by using high-speed dynamic actuation of the lens so as to conform to the pre-determined velocity curve.
The commonly used techniques can be categorized into two groups, characterized respectively in (1) that only the input voltage FMO of the sledge motor is adjusted, and (2) that both the input voltage FMO of the sledge motor and the input voltage TRO of the pick-up head are adjusted, as described in detail as below.
(1) The group for which only the input voltage FMO of the sledge motor is adjusted can be further divided into sub-groups:
A. Velocity-oriented:
In an example with track-jumping number of six thousand (6,000), the voltage value of FMO and acceleration-to-deceleration ratio are adjusted so that the velocity is minimized as the tracking jumping number approaches 6,000. Therefore, the major disadvantages in this art are listed as below:
1) the fact of being unable to achieve the pre-determined track number due to the diversity between devices,
2) large variation of residual track number,
3) device collision as the track number counter is unidirectional, and
4) unstability due to the false estimation of velocity caused by the wobble of pick-up head.
B. Track-jumping number oriented:
The only difference from A is that the track-locking is performed after the pre-determined track number is achieved. However, the major disadvantages in this art are listed as below:
1) the fact of being unable to achieve stable track-locking due to the diversity between devices,
2) dependence of stability upon device quality.
The two methods fail to adjust all the track-jumping conditions with the same parameter, instead a segmental approach is used to perform adjustment. However, such an adjustment approach takes considerable time and programming space.
(2) The group for which both the input voltage FMO of the sledge motor and the input voltage TRO of the pick-up head are adjusted is described as below.
Due to the wobble of the pick-up head, the conventional method as proposed in (1) is unstable. The track-jumping method applied in later developed optical disk drives uses a closed-loop mechanism, characterized in adjusting both the input voltage FMO of the sledge motor and the input voltage TRO of the pick-up head, to eliminate the wobble of the lens.
The driving of the input voltage FMO of the sledge motor is similar to that in method (1). The wobbling signal (A+Bxe2x88x92Cxe2x88x92D) is received from the pick-up head and then is transmitted to the controller and finally the input voltage TRO of the pick-up head is output so as to restrain the wobble of the lens. The driving of FMO reaches more to the pre-determined destination as the damping of the lens is increased. However, the prerequisite is that the pick-up head provides each of the A, B, C and D output signals. Obviously, such method is not suitable for track-jumping with fewer tracks since it is hard to perform track-jumping with small track number even if the lens is completely fixed, only with the sledge motor being active. On the contrary, such method is relatively suitable for track-jumping with more tracks since the sledge motor dominates the whole mechanism while suffering from the problems of friction and narrow frequency band-width.
Furthermore, for a better understanding of the configuration of an optical disk drive, FIG. 1 is presented to illustrate the components interconnected in such device. Please refer to FIG. 1, in which the device comprises an optical disk 1 arranged on the top of an axis motor 2, which is the key component to rotate the disk 1; a pick-up head 3 arranged on a supporting means 4 and being able to moving back and forth on said supporting means 4; and a sledge motor 5 for driving said connected supporting means 4. As shown in FIG. 1, an input voltage TRO provided by said pick-up head 3 and an input voltage FMO provided by said sledge motor 5 are served as controlling signals.
Accordingly, it is a main object of the present invention to provide a high-speed dynamic actuating system for optical disks, particularly useful in an optical disk drive, wherein a closed-loop approach is used to overcome the diversity between devices and thus meet the requirement for high speed track-accessing and solve the problems in that the convention open-loop track-jumping takes a long period of time to perform segmental adjustment.
It is another object of the present invention to provide a high-speed dynamic actuating system for optical disks, wherein the pick-up head is activated by applying high-speed dynamic actuation of the lens so as to conform to the pre-determined velocity curve and eliminate the wobble of the lens caused by different track-jumping times in an optical disk drive and a hard disk.
Moreover, it is a further object of the present invention to provide a high-speed dynamic actuating system for optical disks, wherein said system can be implemented in an integrated circuit (IC), which is directly controlled by the hardware and thus effectively simplify the complicated configuration as in the prior art.
In order to accomplish the foregoing objects, the present invention relates to a high-speed dynamic actuating system for optical disks, with the high-speed dynamic actuation characteristics of the lens fitting to the pre-determined velocity curve, comprising a lens controller, connected to a pick-up head of an optical disk drive for controlling the relative velocity of the lens to said pick-up head; a sledge controller, connected to a sledge motor of an optical disk drive for controlling the relative velocity of said pick-up head to the ground.
The common function of said controllers is to control the relative velocity of the lens to the ground and the high-speed dynamic actuation characteristics of the lens fitting to the pre-determined velocity curve, with both the input of said lens controller and the input of said sledge controller receiving feedback signals from the output of said pick-up head through the feedback loop into both the inputs of said controllers, so as to form a closed feedback loop.
It is preferable that when said controllers perform track-jumping, the difference between the pre-determined velocity and the feedback velocity makes the output signal of said lens controller TRO function, enabling the feedback velocity to follow the pre-determined velocity immediately, and then said sledge controller functions, enabling the velocity of said pick-up head to follow the pre-determined velocity immediately, so as to, on the one hand, minimize the difference between the pre-determined velocity and the feedback velocity and, on the other hand, achieve stable track-jumping.
It is preferable that the feedback loop connects the output of said pick-up head to a track number counter for counting the number of the tracks and then connects said track number counter to both a velocity estimater and a velocity curve fitting circuit that are connected in parallel, with both the outputs of said velocity estimater and said velocity curve fitting circuit connected to perform calculation by a summing element, and then delivered to both the input of said lens controller and the input of said sledge controller, so as to form a closed feedback loop.